A Downing Street source told Sky News the focus is entirely on humanitarian support, with no plans to recall MPs. In recent times, a recall has only been used when military options were on the table.

"The key priority is getting support to people in desperate need," the source said.

Displaced people from the Yazidi sect fleeing the violence in Iraq

The source added Mr Cameron, who is currently on a family summer holiday in Portugal, was "in constant contact with senior ministers and officials" via phone calls and other means.

The Prime Minister is expected to return from the seaside town of Cascais later this week.

Video:Iraq: Should Britain Do More?

Foreign Secretary Philip Hammond, who earlier chaired an emergency meeting to discuss the crisis in Iraq, ruled out any military action in Iraq "at the present time".

"We have a very clear convention about consulting Parliament before British forces are committed into any kind of combat, but we are not talking about that here, we are simply talking about humanitarian actions," he said.

"We don't envisage a combat role at the present time," he added.

The UK has been airdropping aid including tents, food and water in northern Iraq to help tens of thousands of displaced people across the region.

However, Tory backbencher Conor Burns said the Government's action of airdropping supplies in affected areas was "not strong enough" - and asserted the UK should join the US in airstrikes.

The Bournemouth West MP said he was not advocating a ground war, but believed Special Forces should be involved.

"I have been following this really closely for the last couple of weeks but having seen some of the images earlier I was quite seriously overcome," he said.

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Gallery: Thousands Of Iraq Yazidis Displaced

Displaced families from the minority Yazidi community, fleeing the violence in the Iraqi town of Sinjarl, west of Mosul, take refuge in Dohuk province

"These are brother and sister Christians, and this is happening to them in no small part because of our record in Iraq.

"These people are being beheaded by people from IS, and our only response is to drop some food or water on them.

"I think we should be answering positively requests from the Kurds to arm them. I think we should be looking at asylum."

The former head of the army, Lord Dannatt, also backed a parliamentary recall, insisting Britain was "watching in horror" as atrocities were committed.

"In the face of a crisis of this scale, with the potential for so much human misery, this is not the moment for decision-makers to be on holiday," he wrote in the Sunday Telegraph.

Lord Dannatt said it may be necessary to put UK troops on the ground to direct air support.

"The United States in the lead and us in support. We all bear some responsibility," he told the BBC.

Video:Iraq Plunged Into Political Turmoil

"The breakdown in society in Iraq post-2003, we have some culpability for that and so it is difficult for us to say 'Not our problem'."

Tory MPs Nick de Bois and David Burrowes also joined the calls for Parliament to be recalled.

In a letter to Mr Cameron, they said the persecution in Iraq imposed "a moral obligation and a duty to our constituents to reconvene so that the escalating crisis can be properly debated".